Frank Tong, a Vanderbilt University neuroscientist who studies how thoughts are manifested in the brain, said the Neuron study wasn't quite a pure, draw-from-scratch reconstruction. But it was impressive nonetheless, especially for the detail it gathered from measurements that are still extremely coarse.

The researchers' fMRI readings bundled the output of millions of neurons into single output blocks. "At the finer level, there is a ton of information. We just don't have a way to tap into that without opening the skull and accessing it directly," said Tong.